Electric motors



Dec; 3, 1968 D. N. w. BADcocK 3,414,747

' ELECTRIC MoToRs Original Filed April 17, 1964 6 Sheets-Shea?.l 1

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ELECTRIC MOTORS i Original Filed April 1'7, 1964 6 Sheets-Shea?l 5 ,4TTOR/VES D. N. W. BADCOCK ELECTRIC MOTORS Dec. 3, 1968 6 Sheets-Sheet 6Original Filed April 17, 1964 ATTO'QNE United States Patent O 3,414,747ELECTRIC MOTORS David Norman William Badcock, London, England, as-

signor to Kango Electric Hammers Limited, London, England, a Britishcompany Continuation of application Ser. No. 360,630, Apr. 17, 1964.This application Aug. 9, 1967, Ser. No. 659,534 Claims priority,application Great Britain, Apr. 22, 1963, 15,820/ 63 9 Claims. (Cl. S10-50) ABSTRACT F THE DISCLOSURE An electric motor for driving a portablepower tool. The motor has casing end members which -are rigidly butdetachably secured relative to each other and which Ahave bearings toreceive the armature of the motor. A sleeve is disposed axially againstone end member and extends toward the other end member. It is ofelectrically insulating material, and is open at the end nearer theother end member. The sleeve has an internal abutment surface disposedadjacent and facin-g axially away from the one end member. A statorassembly is wholly accommodated within the length of the sleeve -and isin axial abutment with the internal abutment surface. Spring means isprovided between the other end member and the stator assembly to pressthe assembly against the abutment surface within the sleeve -and topress the sleeve iagainst the `abutment sunface within the main housing.The arrangement is such that the various elements are held in place by asingle resilient means and the construction can be dismantled andassembled easily.

This is a continuation of application Serial No. 360,630, filed Apr. 17,19.64, now abandoned.

This invention relates to electric motors and has particular though notexclusive reference to motors for use on portable hammers and likemotorised tools. The main object of the present invention is to providefor simpler land Imore economical construction and assembly of anelectric motor.

According to this invention, there is provided =an insulated electricmotor comprising a motor housing including a mainl housing part Ihavingan opening at one end and having adjacent the other end thereof Ianinternal abutment surface facing towards one end, and a cover detachablysecured to the main housing part at said one end for closing saidopening, and a plurality of coaxially arranged parts disposed within thehousing between said internal abutment on the cover, which partscomprise a locating sleeve made from electrically insulating materialiand capable of insertion in the main housing part through said opening,ywhich sleeve has an abutment surface facing said internalabutmentysurface of the main housing part and has an internal shoulderfacing towards the cover, a stator assembly one end of which is disposedopposite said internal shoulder and the Ltull length of which isaccommodated within the sleeve, saidy assembly being capable of beingremoved from the main housing part and from the sleeve through saidopening, annular spacer means disposed .axially between the statorassembly and the cover and having at opposite ends thereof abutmentsurfaces disposed respectively opposite the cover and the other end ofthe stator assembly and a resiliently axially compressible ring loadingthe parts axially into abutment with the housing, said ring and saidspacer means being capable of removal from the main housing part throughsaid opening.

Some embodiments of the invention will now be de- 3,414,747 PatentedDec. 3, 1968 ice scribed by way of example with reference to theaccompanying drawin-gs in which:

FIGURE l is ta longitudinal section sho-wing the double-insulated motorof a portable percussive tool,

FIGURE 2 is la partial section on line II-II of FIG- 'URE 1,

FIGURES 3 and 4 are cross-sections on lines III- III and IV-IV Of FIGURE1 respectively,

FIGUR-E 5 is 4a fragmentary longitudinal section illustrating a`different embodiment of the invention,

FIGURE 6 is an exploded view showing in perspective some of thecomponents of the motor shown in FIGURE 1,

FIGURE 7 is a perspective view of the insulating sleeve in FIGURE 6,looking 'from the opposite direction,

FIGURE 8 is la perspective view of the pressure ring in FIGURE 6 lookingfrom the opposite direction, and

FIGURE 9 is a perspective view of an air-deflector plate of the Imotor.

The motor illustrated in the accompanying drawings includes a housinghaving an open end and an internal abutment arranged adjacent theopposite end. Assembled within the housing through the open end thereofis a series of coaxially aranged parts including a sleeve formed ofinsulating material having at one end an external shoulder which coactswith the abutment. A stator assembly is housed within the sleeve withone end abutting an internal shoulder `formed on that end of the sleevehaving the external shoulder. A pressure ring abuts the other end of thestator assembly. The several partsare retained in the housing by aclosure means which is attached to the open end of the housing iand theparts are held under axial loading by an axially compressible ring whichmay comprise one or more waved washers and which is compressed when theclosure means is secured in place. The compressible ring may bepositioned between the pressure ring and a spacing ring which `abuts theclosure means or alternatively between the internal abutment on thehousing and the external shoulder on the sleeve.

As shown more particularly in FIGURES 1, 2, 7 and 8 the stator-enclosingsleeve 1 (which is moulded in a suitable plastic or like insulatingmaterial) comprises a main hollow body portion 2 of generallycylindrical form, but having parallel flat walls 3, 3A (the latterhaving one or a series of holes 4) and a cylindrical end spigot 5 havingan external diameter of substantially the same dimension as the distancebetween the outer faces of said at walls 3, 3A.

An interrupted shoulder 6 provided yat the spigot end of the sleeve 1 isadapted to seat against an internal abutment 8 in the cylindrical shell9 of the housing 10, with or without an intervening metal abutment ring(not shown). Such ran abutment ring could convenient-ly be of C-shape toprovide a gap to accommodate therewithin the fiat-top 11A of a liner 11in an adjacent switch chamber 129. The holes 4 in :flat wall 3A ofsleeve 1 are provided with bushes 7 (FIGURE 2) for the passagetherethrough of conductor or lead wires '13 from the eld coil 12 of aflat-sided stator assembly 14, said lead wires 13 also passing throughsuitable openings in liner 11 to the motor switch 117 therein. Thesleeve 1 may be held against langular displacement in any suitablemanner, such as by means of an inwardly projecting pin carried byhousing shell 9 and engaging between a pair of longitudinal ribs 85Amoulded on sleeve 1.

The abutment 8 which forms a seating for the shoulder 6 of sleeve 1locates that end of said sleeve a suitable distance away from the endwall 15 of housing 10 to leave a space 17 occupied by a conventional fan18. The end wall may be and preferably is formed integral with thehousing shell 9 to form a pot-shaped one-piece housing, uninterrupted byinternal lugs or wide internal flanges as normally provided to receivestator clamping screws.

Within a central bore 15A in end wall 15 is a bearing unit 19 ofcartridge form, which is adapted to support one end of the shaft 20 ofmotor armature 21. If desired the motor armature 21 may be of doubleinsulated type. The bearing unit 19 comprises a cartridge shell 22having a flange 23 by means of which it may `be suitably secured to saidwall 15 by screws 24 inserted from the outside of the wall, saidcartridge shell 22 enclosing a ball bearing assembly 35 coacting withthe armature shaft 20 and backed up on one side by a pack of Bellevillewashers 25 or the like. On the other side of ball bearing assembly is asuitable seal 36; the bearing cartridge shell 22 is formed so as toprovide an oil-sealed bearing unit. In the extremity of shaft 20 isscrewed a tapered pinion 26 to transmitting a rotary drive to associatedmechanism for reciprocating a driver (not shown) the projecting bearingunit 19 serves to locate a mounting plate 86 for the driver mechanism,which however forms no part of the present invention. The drivermechanism is housed in a main body or casing 92 to which the motorhousing 10 is suitably attached.

At the other or outer end of the body 2 of sleeve 1 is located apressure ring 27 having a radial flange 28, said ring 27 beingpreferably made as a moulding in plastic or other electrical insulatingmaterial. Projecting axially from one side of ange 28 is a cuff 29 whichis adapted to fit snugly within the neighbouring end of sleeve 1 toprevent relative rotation, and accordingly the cuff 29 is contoured (asshown more clearly in FIGURE 8) to conform with the flat-sided shape ofsleeve body 2. The cuff 29 is adapted to press the stator assembly 14against the internal shoulder 6A of sleeve 1 and thus the externalshoulder 6 of sleeve 1 firmly against abutment 8 in the motor housing10; a number of circumferentially spaced lugs 6B inwardly projectingfrom shoulder 6A coact with the flat-sided stator assembly 14 to hold itagainst rotation. A spigot 29A projects from the other side of pressurering flange 28, and said spigot 29A is wholly or partly of circular formto serve as a location seating for one or more waved washers 30 asshown, or equivalent spring means located adjacent the shell 9 of motorhousing 10, and adapted to function as means for applying axialpressure. Other forms of axially compressible rings may comprise aseries of separate circumferentially spaced spring elements carried by aring-like support or a ring of resilient or slightly compressiblemetallic or non-metallic material.

The axially compressible washers 30 or other spring means expand betweenthe pressure ring 27 and a spacer element bearing directly or indirectlyagainst an abutment, such as provided by a cover for the pot-likehousing 10, thereby firmly clamping sleeve 1 and the enclosed statorassembly 14 endwise without recourse to fixing screws or otherfasteners. In this particular embodiment the spacer element forms partof a brush assembly 50 contained in the -mouth end 16 of housing shell9.4That is, the spacer element here takes the form of a brush mountingring 51 of plastic or other suitable electrical insulating material; ifdesired a tough washer (not shown) may be interposed between the brushmounting ring 51 and the waved washer(s) 30 which seat against flange 28of pressure ring 27. The brush assembly 50 may be held in position -by aseparate detachable cover-if desired with a disc or retaining ring (notshown) of suitable insulating material interposed between the brushassembly 50 and the cover; preferably, however, as described later, thiscover forms an integral part, that is, it is the base 101 of a handleassembly 100 for the portable tool.

The mouth end 16 of housing shell 9 is necessarily counterbored toreceive the radial flange 28 of pressure ring 27 and this allows amplespace for the ready insertion of the sleeve 1 and the stator assembly14. Diametrically opposite parallel faces 37 and 37A are provided withinthe pressure ring 27 but these terminate before reaching the rim 171 ofthe cylindrical spigot 29A. The ring 27 and the circumferentialclearances between faces 37 and 37A form through air passages forventilation. The handle base 101- forming a cover for the pot-likehousing 10-has air vents 150 and air openings 38 are provided adjacenthousing end wall 15.

The end of armature shaft 20 adjacent the motor commutator 33 isjournalled in the housing cover, that is, handle base 101, in a suitablebearing assembly 34, spring loaded in a manner similar to that used inbearing unit 19, except that it is preferred to substitute a more highlycompressible spring means, such as a helical coil spring 39, for thepack of Belleville washers 25.

In the modification shown in FIGURE 7, which illustrates part of adifferent portable tool, the axially compressible ring is shown arrangedin a different position in the series of abutting parts assembled in themotor housing 10A. As shown, an insulating sleeve 42 is employed whichmay be somewhat similar in shape to the insulating sleeve 1 alreadydescribed, or at least has a reduced neck or spigot 43 providing anexternal shoulder 44 forming a seating for a backing ring 45. One ormore waved washers 30 or equivalent spring means to provide axialpressure are interposed between said backing ring 45 and an internalflange 46 in the housing. This arrangement has independently mountedbrush units 48 so that the brush assembly mounting ring as previouslydescribed is not required. Instead the pressure ring 47 abuts directlyagainst the closure member 40.

The brush assembly 50 is shown more particularly in FIGURES 2 and 4.

The brush mounting ring 51 of the brush assembly 50 is provided withintegral diametrically-opposite main bosses 52.

Mounting ring 51 is formed with a flange 54 to facilitate locationwithin the mouth end 116 of the motor housing 10 and the periphery 55 ofthe ring 51 has a series of longitudinally extending ribs 56, preferablyequi- -distantly spaced circumferentially, which do not project outradially beyond the rim of flange 54 but which do project endwise beyondthe other side face 57, thereby forming a series of gaps 58 forventilation purposes; these ribs 56 are so arranged as to block theingress of implements or other metallic parts which might accidentallycontact with electrically alive components.

To ensure accurate angular disposition of the support 50 and to guardagainst post-assembly displacement a screw (not shown) may be providedon the crest of one of the ribs 56, said screw engaging a suitablegroove in the motor housing bore.

The brushes 82 are of conventional rectangular-section form and areslidable in the shaped bores of cylindrical brass brush holders 61carried in flanged bushes 62 made of insulating material. The holders-61 are force tits in the bushes 62, which are screw-threaded to receivescrewon caps 63 which, when assembled, overlap the bushes 62. Thebrushes 82 are biased into rubbing contact with the commutator 33 bycompression springs 83 having contact shoes 84 which abut the caps 63.The bushes 62 are adapted to be clamped within the diametrical alignedbores 64 of main bosses 52 by parallel-sided straps 65 (of metallic orof insulating material) fitted into slots 66 respectively and held byscrews 67.

From the ends of holders 61 which project inwardly beyond the bushes 62,there extend, substantially at right angles to the brush axis, brassterminal pillars 68 which are brazed onto brush holders 61 and arefurnished with heads (conveniently of cubical form) which are receivablewithin recesses in insulating terminal housings 71 (conveniently plasticmouldings). The shanks of pillars 68 passes through side notches 72 inhousings 71 which have integral cylindrical spigots received in holes inring 51.

The eyed ends of sleeved leads 76 from a motor field coil pass throughnotches 72 alongside of pillars 68 and are firmly secured by terminalscrews 77 which engage tapped holes 78 in the pillar heads 69. Access tothe brushes 82 and their holders 61 is afforded through openings 88 inbosses 89 formed on the exterior of the motor housing 10, said openings88 being normally closed by discs 90 held by circlips 91.

An air deflector plate 157 for ventilation of the 'brush assembly isprovided with a centrally apertured hub which is adapted to encircle aboss 154 partly housing the bearing assembly 34 adjacent the commutator33 of the motor, and partly overlapping an insulated shroud 149. The airdeflector plate 157 has a series of radiating lugs 158, preferablyequidistantly spaced and of a number and outline form to match theradial ribs 56 on the brush mounting ring 51, strengthening Webs 152extending from said lugs 158 to the hub, One of the lugs 158 is providedwith an aperture 159 to receive a locating pin 155 projecting inwardsfrom the handle base 101; the -pin 155 preferably passed right throughsaid aperture 159 to engage and thus locate the brush mounting ring 51.

Air flowing into the brush end of the motor housing through slots 150 inthe handle base 101 has to pass either over` the rim 160 of thedeflector plate 157, between the lugs 158, or through air slots 161 insaid plate 157 which are arranged so as not to register with the airslots 150 in the handle base 101, so that an implement or other articleinserted through one of the slots 150 is arrested by plate 157, andcannot touch electrically live parts.

The plate 157 also serves another purpose, that is, recessed boxes 162are provided in said plate and have holes 163 to receive stud-headbuttons 1-65 forming integral parts of moulded silicone rubber pads 166.These pads 166 are adapted to apply end clamping pressure on the heads-69 of the terminal pillars 68 and on portions 0f the field coil leads76. The radial lugs 158 of deflector plate 157 are clamped against theface of the handle base 101 by the ribs 56 of the brush mounting ring51.

The handle assembly 100 of the portable tool (FIG- URE 1) of thedrawings comprises the base 101 adapted to serve as a cover for one endof the motor housing as already referred to, a spigot 103 being providedon said base 101 for location within the open end of the motor housing10. The base 101 is fastened to motor housing 10 by screws 93 (seeFIGURES 3 and 4).

The hand grip 104 comprises a tube connected to the base 101 by a solidweb 106 at one end and by a hollow webed pillar 107 at the other end; apart of said grip tube 104 may be partially or completely enclosed in asheath (not shown) 0f moderately resilient rubber or the like.

Within the grip tube 104 is accommodated the major part of an operatinglever 109 rockable on any intermediate cross-pin 110, the longer portionof lever 109 having a head 111 adapted to project through a longitudinalslot 112 in the grip tube 104. The tail 113 of lever 109 carries anadjustable screw stop 114 adapted to apply pressure, through a leafelement 105 hinged on an integral projection 108, to one end of aplunger 115 slidable within the bore of pillar 107, and thus compensatefor manufacturing variations in the various components concerned withswitch operation.

A cable entry assembly 116 is aligned with the plunger 115 and preventsin-line mechanical connection with a switch 117 contained in the switchchamber 129 of the motor housing 10.

The cable entry assembly 116 comprises a cable end housing 118 made of asuitable insulating material and having a tubular spigot 119 receivablewithin a hole 120 in motor housing 10, a resilient sheath 121 ascustomarily employed on the end of a trailing power cable beingreceivable within the bore of housing 118. The cable end housing 118 isflanged to enable it to be secured to motor housing 10.

For securing cable sheath 121 in position a locking bridge 124, alsomade 0f insulating material, is adapted to be secured, by screws (notshown) to housing 118 so that a block 126 on said bridge enters athrough slot 127 in the housing 118 to bear against sheath 121. The endof the power cable (not shown) is passed through an angled protectiveduct 128 of insulating material to enable the cable ends to be connectedto switch 117.

A pair of rods 131 made of insulating material and connected together atopposite ends by tie bars 132 and 132A extend through parallel holes 133in motor housing 10, at opposite sides of the hole which receives thecable end housing spigot 119.

The tie bar 132 is engaged by plunger 115 as it is projected underdirect action of operating lever 109 in hand grip 104, thereby todisplace rods 131 and, through tie bar 132A and a strut 134, to move theoperating member or tumbler 135 to operate switch 117. The switch 117may be of such a construction that it would remain on if pressure onlever 109 is relieved, another gripping action on said lever beingrequired to project plunger 115 forward again to switch off switch 117.

For double-insulating purposes a moulded box-like liner 11 of insulatingmaterial is secured in the switch chamber 129 and is suitably aperturedfor the passage of Various components which project into said liner. Theswitch chamber 129 is made without a roof, so that the flat top 11A ofliner 11 is exposed in the interior of motor housing 10 and lies inclose proximity to the stator assembly 14, whilst outward projection ofthe switch chamber is reduced to a minimum.

The liner 11 is held in switch chamber 129 in any suitable manner, suchas by pressure applied through rubber blocks by abutment strips 136 in aswitch chamber cover 138, or by a liner 139 in said cover; the liner 11has integral side blocks 140, to which switch 117 may be secured by thescrews which force it onto the resilient mountings 141.

What is claimed is:

1. An electric motor for a portable power tool comprising a motorhousing including a main housing Ipart having an opening at one end andhaving adjacent the other end thereof of an internal abutment surfacefacing towards said one end, and a cover rigidly detachably secured tothe main housing part at said one end for closing said opening, and aplurality of coaxially arranged parts disposed within the housingbetween said internal abutment and the cover, which parts comprise alocating sleeve made from electrically insulating material and capableof insertion in the main housing part through said opening, which sleevehas an abutment surface facing said internal abutment surface of themain housing part and has an internal shoulder facing towards the cover,a stator assembly one end of which is disposed opposite said internalshoulder and the full length of which is accommodated within the sleeve,said assembly being capable of being removed from the main housing partand from the sleeve through said opening, annular spacer means disposedaxially between the stator assembly and the cover and having at oppositeends thereof abutment surfaces disposed respectively opposite the coverand the other end of the stator assembly, and a resiliently axiallycompressible ring loading the parts axially and being a single means forurging said parts into abutment with the housing, said ring and saidspacer means being capable of removal from the main housing part throughsaid opening.

2. An electric motor as claimed in claim 1, wherein the axiallycompressible ring is interposed between the internal abutment surface inthe main housing part and the facing abutment surface on the sleeve.

3. An electric motor as claimed in claim 1, in which said sleevecomprises a main body of generally opposed cylindrical shaped wallportions and having flat parallel walls connecting said cylindrical wallportions and dening therewith a space for receiving the stator assembly,

the stator assembly having flat sides, and a cylindrical end spigothaving an external diameter of substantially the same dimension as thedistance between the outer faces of said flat walls, the said main bodyand end spigot defining between them an external shoulder which providesthe abutment surface for coacting with said internal abutment surface inthe main housing part.

4. An electric motor as claimed in claim 3 in which said sleeve has apair of spaced external longitudinal ribs, and said housing has aninternal lprojection thereon with which said ribs engage to preventrotation of said sleeve.

5. An electric motor comprising a motor housing including a main housingpart haa/ing an opening at one end and having adjacent the other endthereof an internal abutment surface facing towards said one end, and acover rigidly detachably secured to the main housing part at said oneend for closing said opening, a locating sleeve made from electricallyinsulating material and capable of insertion in the main housing partthrough said opening, which sleeve is in axial abutment with saida-butment surface and has an internal shoulder facing towards the cover,a stator assembly one end of which is disposed in abutment with saidshoulder and the full length of which is accommodated Within the sleeve,and spacer means extending between the cover and the other end of thestator assembly, which spacer means comprises a pressure ring disposedadjacent the end of the sleeve nearer the cover and abutting the otherend of the stator assembly axially, an annular brush-bearing spacerdisposed within the main housing part in operative axial abutment withthe cover, brushes for the motor which brushes are mounted in thespacer, and resilient means disposed between the spacer and the pressuremember for urging the pressure member, the stator assembly and thesleeve away from the cover and urging the spacer towards the cover, andmeans locating the spacer against rotation about the motor axis relativeto the housing, the housing having an aperture formed therein oppositeeach brush for affording access to that brush.

6. A motor as claimed in claim 5, wherein the spacer is made from anelectrically insulating material.

7. An electric motor as claimed in claim 5, in which said pressure ringhas a radial flange and a cul projecting axially from one side thereofand abutting the end of the stator assembly, said cuff having a shapeconforming to the internal shape of said sleeve and fitting snuglytherein.

8. An electric motor for driving a portable power tool comprising meansproviding casing end members which are rigidly but detachably securedrelative to each other and respectively having bearings for an armatureof the motor, and a sleeve portion disposed axially against one of theend members and extending towards the other of the end members, whichsleeve portion is made from an electrically insulating material, is openat its end nearer said other end member, and has an internal abutmentsurface disposed adjacent and facing axially away from said one endmember, a stator assembly in axial abutment with said internal abutmentsurface and wholly accommodated within the length of the sleeve whichassembly can be inserted into and removed from the sleeve through saidopen end of the sleeve, and spring means acting between said other endmember and the stator assembly and being a single means urging theassembly resiliently against said abutment surface.

9. An electric motor for a portable power tool, comprising a mainhousing part which has adjacent one end thereof an internal axiallyfacing abutment surface and at its other end an opening, a sleeve madefrom electrically insulating material and capable for assembly anddismantling purposes of insertion and removal through said opening,which sleeve abuts said abutment surface and has an internal abutmentsurface facing said opening, an armature assembly disposed in abutmentwith said internal abutment surface of the sleeve and wholly within thesleeve, a cover rigidly and detachably mounted on said main housing partfor closing off said opening, and spring means acting between the coverand the armature assembly and being a single means to press the assemblyagainst the abutment surface within the sleeve and to press the sleeveagainst said abutment surface within the main housing part.

No references cited.

MILTON O. HIRSHFIELD, Primary Examiner. G. NUNEZ, Assistant Examiner.

